Technical Field
The present invention relates to semiconductor processing, and more particularly to fabricating light emitting diodes using a transfer process to reduce processing time, increase transmissibility and improve performance.
Description of the Related Art
Top emission organic light emitting diodes (OLED) are typically fabricated with a top electrode formed using a vacuum process. Top emission OLEDs with a high transmission top electrode for light out-coupling are difficult to fabricate since the vacuum processes often lead to surface damage on the top electrode. This surface damage has an impact on the transmissibility of the top electrode. In addition, vacuum processes tend to be time consuming, which increases expense. Further, since vacuum processes provide materials on bottom or underlying layers, the type of materials selected are limited due to material compatibility issues.
Examples of vacuum processes described below suffer from additional drawbacks. For example, sputtering deposition can significantly damage the underlying layer or layers on which the sputtered material is formed. Humidity during an atomic layer deposition (ALD) process can lead to a degradation in the properties of existing layers. Chemical deposition processes can cause additional unwanted reactions with the existing layers. Evaporation processes take a long time to introduce a multilayer structure, and also reduce the transmission for transparent conducting electrodes.
Even solution processes top electrodes, such as, solution processed transparent conductive oxides (TCO) can degrade the transmissibility of the top electrode. Such processes also require high temperature annealing, which limits the material alternatives for the bottom layers, to achieve good conductivity.